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A measurement of the b quark fragmentation function at {radical}Q{sup 2} = 45.6 GeV

Description: Presented here is a measurement of the b quark fragmentation function D{sub b}(X), taken from a sample of 504 semi-leptonic B decays which were selected from the 150,000 Z{sup 0} decays collected between 1993 and 1995 at the SLD at SLAC. The energy of each tagged B hadron is reconstructed using missing jet energy, based on the information from the lepton and a partially-reconstructed charm-decay vertex. Account is taken of the effect of primary orbitally excited mesons (B**s). An iterative unfolding procedure is used which serves to effectively extract the true fragmentation function from the reconstructed B energy spectrum. The final result is shown to be compatible with many theoretical models. A comparison is made with other b fragmentation function measurements at 45.6 GeV, and this measurement is shown to be consistent with those results. The average scaled energy is found to be (x{sub E}) = 0.697{+-} 0.017(stat) {+-} 0.034(sys).
Date: June 1, 1996
Creator: Church, E.D.
Partner: UNT Libraries Government Documents Department

Collective instabilities of the 50-50 GeV Muon Collider

Description: Single bunch instabilities for the 50-50 GeV muon collider are discussed. An impedance budget for the collider is estimated. An {vert_bar}{eta}{vert_bar} = 1 x 10{sup -6} is desired to avoid excessive rf systems. Potential-well distortion can be compensated by rf cavities. Longitudinal microwave growth can be reduced by smoothing the bunch distribution before injection. Transverse microwave instability can be damped by chromaticities and octupoles. Beam breakup can be cured by BNS damping in principle, but is nontrivial in practice. More detailed discussions are given in Ref. 1.
Date: April 19, 1999
Creator: Ng, K.Y.
Partner: UNT Libraries Government Documents Department

Jefferson Lab CEBAF energy upgrade plans

Description: This paper presents interim conceptual plans for upgrading the Continuous Electron Beam Accelerator Facility (CEBAF) at the Thomas Jefferson National Accelerator Facility to extend Jefferson Lab's world leadership in nuclear physics research. The CEBAF accelerator was designed in the mid-1980's to provide beams of electrons at an energy of 4 GeV (billion electron volts) for use as probes of the atom's nucleus in CEBAF's three experiment halls. As of early 1999, the accelerator exceeds its design energy by routinely operating above 5.5 GeV. When upgraded, it will provide 11 GeV electron beams for studies in existing experimental halls and 12 GeV electrons to generate photon beams for related but qualitatively different nuclear studies in a new Hall D.
Date: August 1, 1999
Creator: Rode, C. H.; Benesch, J.; Chao, Y.; Delayen, J. R.; Karn, J.; Mammosser, J. et al.
Partner: UNT Libraries Government Documents Department

Tolerable Beam Loss at High-Intensity Machines

Description: Tolerable beam losses are estimated for high-intensity ring accelerators with proton energy of 3 to 16 GeV. Dependence on beam energy, lattice and magnet geometry is studied via full Monte Carlo MARS14 simulations in lattice elements, shielding, tunnel and surrounding dirt with realistic geometry, materials and magnetic fields.
Date: August 28, 2000
Creator: Oleg E. Krivosheev, Nikolai V. Mokhov
Partner: UNT Libraries Government Documents Department

The JLAB Research Program with the 12 GeV Upgrade

Description: The plans for upgrading the CEBAF accelerator at Jefferson Lab to 12 GeV are presented. The research program supporting that upgrade are illustrated with a few selected examples. The instrumentation under design to carry out that research program is discussed.
Date: May 1, 2001
Creator: Jager, Kees de
Partner: UNT Libraries Government Documents Department

Development of an upgrade of the CEBAF acceleration system

Description: Long-term plans for CEBAF at Jefferson Lab call for achieving 12 GeV in the middle of the next decade and 24 GeV after 2010. Such energies can be achieved within the existing footprint by fully populating the accelerator with cryomodules capable of providing 3 to 4 times as much voltage as the design value of the existing ones within the same length. In particular, this requires the development of superconducting cavities capable of operating at gradients above 12 MV/m and Q close to 10{sup 10}.
Date: August 1, 1998
Creator: Delayen, J.R.
Partner: UNT Libraries Government Documents Department

High Current, Long Beam Pulse with SLED

Description: A proposed, high charge, fixed target experiment (E-158) is planned to run with the highest possible energies available at the Stanford Linear Accelerator Center (SLAC), at 45 and 48 Gev. The charge is up to 6 {center_dot} 10{sup 11} particles in a 370 ns long beam pulse. The SLAC Energy Development (SLED) rf system generates an increasing no-load beam energy, with a linearly decreasing slope. We show how to obtain a current variation that tracks the no-load voltage, resulting in zero energy spread. We discuss the results of a lower energy experiment that verifies the predicted charge and current at the energies required for E-158.
Date: April 16, 1999
Creator: Decker, Franz-Josef
Partner: UNT Libraries Government Documents Department

CEBAF at 12 and 25 GeV

Description: The US nuclear physics community has identified an upgrade of CEBAF to 12 GeV as one of its top priorities. The principal motivation is to enable meson spectroscopy with 9 GeV polarized, quasi-monochromatic photons. A plan for implementing the 12 GeV upgrade has been prepared. Subsystem designs are being tested. Additional opportunities to reduce total project costs have been identified and will be pursued. The plan now calls for the addition to CEBAF of 10 new high-performance cryomodules and a new recirculation arc, yielding 12 GeV after 5.5 passes through the accelerator. Formal construction start could be in 2006. The same cryomodule design would subsequently be the building block for an eventual upgrade to 25 GeV.
Date: September 1, 2001
Creator: Harwood, Leigh & Reece, Charles
Partner: UNT Libraries Government Documents Department

Beam Profile Measurement at 30 GeV Using Optical Transition Radiation

Description: We present results of measurements of spot size and angular divergence of a 30 GeV electron beam through use of optical transition radiation (OTR). The OTR near field pattern and far field distribution are measured as a function of beam spot size and divergence at wavelengths of 441, 532, and 800 nm, for both the single and double foil configurations. Electron beam spot sizes of 50 {micro}m rms have been resolved, demonstrating the utility of OTR for measurement of small beam spot sizes of high energy (30 GeV) electron beams. Two-foil interference was clearly observed and utilized electron beam angular divergences of {approximately} 100 {micro}rad.
Date: July 10, 1999
Creator: Whittum, David H
Partner: UNT Libraries Government Documents Department

Precision measurement of the neutron spin dependent structure functions

Description: In experiment E154 at the Stanford Linear Accelerator Center the spin dependent structure function g{sub 1}{sup n} (x, Q{sup 2}) of the neutron was measured by scattering longitudinally polarized 48.3 GeV electrons off a longitudinally polarized {sup 3}He target. The high beam energy allowed the author to extend the kinematic coverage compared to the previous SLAC experiments to 0.014 {le} x {le} 0.7 with an average Q{sup 2} of 5 GeV{sup 2}. The author reports the integral of the spin dependent structure function in the measured range to be {integral}{sub 0.014}{sup 0.7} dx g{sub 1}{sup n}(x, 5 GeV{sup 2}) = {minus}0.036 {+-} 0.004(stat.) {+-} 0.005(syst.). The author observes relatively large values of g{sub 1}{sup n} at low x that call into question the reliability of data extrapolation to x {r_arrow} 0. Such divergent behavior disagrees with predictions of the conventional Regge theory, but is qualitatively explained by perturbative QCD. The author performs a Next-to-Leading Order perturbative QCD analysis of the world data on the nucleon spin dependent structure functions g{sub 1}{sup p} and g{sub 1}{sup n} paying careful attention to the experimental and theoretical uncertainties. Using the parameterizations of the helicity-dependent parton distributions obtained in the analysis, the author evolves the data to Q{sup 2} = 5 GeV{sup 2}, determines the first moments of the polarized structure functions of the proton and neutron, and finds agreement with the Bjorken sum rule.
Date: February 1, 1997
Creator: Kolomensky, Y.G.
Partner: UNT Libraries Government Documents Department

Superconducting Cavity Development for the CEBAF Upgrade

Description: Long-term plans for CEBAF at Jefferson Lab call for achieving 12 GeV in the middle of the next decade and 24 GeV after 2010. In support of these plans, an Upgrade Cryomodule, capable of providing more than twice the operating voltage of the existing CEBAF modules within the same length, is being developed. In particular, this requires the development of superconducting cavities capable of consistently operating at gradients above 12 MV/m and Q {approximately} 10{sup 10}. We have engaged in a complete review of all the processes and procedures involved in the fabrication and assembly of cavities, and are modifying our chemical processing, cleaning, and assembly facilities. While we have retained the cell shape of existing CEBAF cavities, the new superconducting structure will be substantially different in several respects, such as the higher-order-modes damping and the fundamental power coupling systems. Design features and experimental results will be presented.
Date: March 1, 1999
Creator: Campisi, I.E.; Delayen, J.R.; Doolittle, L.R.; P.Kneisel; Mammosser, J. & Phillips, L.
Partner: UNT Libraries Government Documents Department

Fixed field circular accelerator designs

Description: The rapid rate and cycle time required to efficiently accelerate muons precludes conventional circular accelerators. Recirculating linacs provide one option, but the separate return arcs per acceleration pass may prove costly. Recent work on muon acceleration schemes has concentrated on designing fixed-field circular accelerators whose strong superconducting fields can sustain a factor of 4 increase in energy from injection to extraction. A 4 to 16 GeV fixed-field circular accelerator has been designed which allows large orbit excursions and the tune to vary as a function of momentum. Acceleration is .6 GeV per turn so the entire cycle consists of only 20 turns. In addition, a 16 to 64 GeV fixed-field circular accelerator has been designed which is more in keeping with the traditional Fixed Field Alternating Gradient machines. In this work the two machine designs are described.
Date: January 6, 2000
Creator: Johnstone, C.; Wan, W. & Garren, A.
Partner: UNT Libraries Government Documents Department

Frequency tuning of the CEBAF upgrade cavities

Description: Long-term plans for CEBAF at Jefferson Lab calls for achieving 12 GeV in the middle of the next decade and 24 GeV after 2010. In support of these plans, an Upgrade Cryomodule capable of providing more than twice the voltage of the existing ones is under development. One requirement is to operate the superconducting cavities, which are 40% longer than existing ones, at 2.5 times the original design gradient with the same amount of rf power. This puts stringent requirements on the accuracy of the frequency tuner: range of 400 kHz and resolution of 1 Hz. A new tuner design to meet these requirements is under development. This system avoids problem areas of previous designs by holding to the principles of not placing moving parts in the vacuum and/or low temperature space, and of having all drive components readily accessible for maintenance and replacement without cryomodule warm-up.
Date: March 1, 1999
Creator: Delayen, J.R.; Doolittle, L.; Feldl, E.; Nguyen, V. & Sachleben, W.
Partner: UNT Libraries Government Documents Department

An R.F. Input Coupler System for the CEBAF Energy Upgrade Cryomodule

Description: Long term plans for CEBAF at Jefferson Lab call for achieving 12 GeV in the middle of the next decade and 24 GeV after 2010. Thus an upgraded cryomodule to more than double the present voltage is under development. A new waveguide coupler system has been designed and prototypes are currently being developed. This coupler, unlike the original, has a nominal Q{_}ext of 2.1 x 10{sup 7}, reduced sensitivity of Q{_}ext to mechanical deformation, reduced field asymmetry within the beam envelope, freedom from window arcing with a single window at 300 K, and is capable of transmitting 6kW CW both traveling wave and in full reflection.
Date: March 1, 1999
Creator: Delayen, J.R.; Doolittle, L.R.; Hiatt, T.; Hogan, J.; Mammosser, J.; Phillips, L. et al.
Partner: UNT Libraries Government Documents Department

MULTI-GeV GLUONIC MESONS

Description: Lattice QCD gives reliable predictions for hybrid charmonium and multi-GeV glueball masses. Proton-antiproton annihilation may offer an excellent opportunity for the first observation of these states. There are two distinct possible programs: The search for J{sup PC}-exotic and non-J{sup PC}-exotic states. The latter program represents substantially higher cross sections and does not absolutely require partial wave analysis, two very attractive features. The program can be performed with a varying {bar p} energy < 10 GeV and a fixed target.
Date: June 1, 2001
Creator: PAGE, P.R.
Partner: UNT Libraries Government Documents Department

Lattice design for a 50 on 50-GeV muon collider

Description: Two modes are being considered for a 50 on 50-GeV muon collider: one being a high-luminosity ring with broad momentum acceptance (dp/p of {approximately} 0.12%, rms) and the other lower luminosity with narrow momentum acceptance (dp/p of {approximately} 0.003%, rms). To reach the design luminosities, the value of beta at collision in the two rings must be 4 cm and 14 cm, respectively. In addition, the bunch length must be held comparable to the value of the collision beta to avoid luminosity dilution due to the hour-glass effect. To assist the rf system in preventing the bunch from spreading in time, the constraint of isochronicity is also imposed on the lattice. Finally, the circumference must be kept as small as possible to minimize luminosity degradation due to muon decay. Two lattice designs will be presented which meet all of these conditions. Furthermore, the lattice designs have been successfully merged into one physical ring with mutual components; the only difference being a short chicane required to match dispersion and floor coordinates from one lattice into the other.
Date: January 6, 2000
Creator: Johnstone, C.; Wan, W. & Garren, A.
Partner: UNT Libraries Government Documents Department

Development of a cryomodule for the CEBAF upgrade

Description: Long-term plans for the CEBAF at Jefferson Lab call for achieving 12 GeV in the middle of the next decade and 24 GeV after 2010. In support of those plans, an Upgrade Cryomodule, capable of providing more than three times the voltage of the original CEBAF cryomodule specification within the same length, is under development. In particular, this requires the development of superconducting cavities capable of consistently operating at gradients above 12 MV/m and Q{approximately}10{sup 10}, new frequency tuners with excellent resolution, and cavity control systems.
Date: December 1, 1999
Creator: Team, J. Delayen for the Upgrade Cryomodule Development
Partner: UNT Libraries Government Documents Department

Investigation of high-energy-proton effects in aluminum

Description: Specimens of 1100 aluminum were exposed to several fluences of 23.5-GeV protons at the Brookhaven Alternating Gradient Synchrotron. Although this energy is above those currently being proposed for spallation-neutron applications, the results can be viewed as indicative of trends and other microstructural evolution with fluence that take place with high-energy proton exposures such as those associated with an increasing ratio of gas generation to dpa. TEM investigation showed significantly larger bubble size and lower density of bubbles compared with lower-energy proton results. Additional testing showed that the tensile strength increased with fluence as expected, but the microhardness decreased, a result for which an intepretation is still under investigation.
Date: December 1, 1997
Creator: Czajkowski, C.J.; Snead, C.L. Jr. & Todosow, M.
Partner: UNT Libraries Government Documents Department

Upgrade of the CEBAF acceleration system

Description: Long-term plans for CEBAF at Jefferson Lab call for providing 12 GeV in the middle of the next decade and 24 GeV after 2010. Such energies can be achieved within the existing footprint by fully populating the accelerator tunnel with cryomodules capable of twice the operating voltage of the existing ones within the same length. In particular, this requires the development of superconducting cavities capable of operating at gradients above 12 MV/m and Q{approximately}10{sup 10}. An R&D program for the development of the cryomodules is under way and will be presented, as well as various options for the upgrade path.
Date: March 1, 1999
Creator: Team, J.R. Delayen for the Upgrade Cryomodule Development
Partner: UNT Libraries Government Documents Department

Cryomodule development for the CEBAF upgrade

Description: Long term plans for CEBAF at Jefferson Lab call for achieving 12 GeV in the middle of the next decade and 24 GeV after 2010. In support of these plans, an Upgrade Cryomodule capable of providing more than three times the voltage of the original CEBAF cryomodule specification within the same length is under development. Development activities have been focused on critical areas thought to have maximum impact on the overall design. These have included the cavity structure, rf power coupling, cavity suspension, alignment, cavity tuning, and beamline interface. It has been found that all design and development areas are tightly coupled and can not be developed independently. Substantial progress has been made toward an integrated design for the Jefferson Lab Upgraded Cryomodule.
Date: March 1, 1999
Creator: Delayen, J. R.; Doolittle, L. R.; Feldl, E.; Hogan, J.; Mammosser, J.; Nguyen, V. et al.
Partner: UNT Libraries Government Documents Department

Comments on momentum aperture of 100 GeV/n Au runs in RHIC

Description: In RHIC 2010 100 GeV/n Au run, the momentum aperture has been an issue in the re-bucketing and the beam intensity lifetime in store. Both Blue and Yellow beams with comparable storage RF voltage and peak current have suffered more beam loss than in Run 2007. In this note, some comments are made for the momentum aperture of the lattices used from the Au runs in 2007, 2008 and 2010. From the wigglings and the beam decays of each lattice, information regarding the machine momentum aperture is presented. Several directions in further improvement are discussed.
Date: November 1, 2011
Creator: Zhang, S.Y.
Partner: UNT Libraries Government Documents Department